What makes a PSU bad, exactly?

[TheMirageOfDeceit]

Can someone explain to me what exactly makes the corsair cx series psu bad, for example?

 

[The Paladin]

bad isn't the right word, low quality , is the right one, in the same way that a chevy cleo and a BMW M5 are cars but the cleo is of lower quality, can it do the same job as the BMW , sure to a point and then will break down.

the problem with a PSU of lower quality is when they fail.. they tend to take out motherboards, video cards, memory ram even hard drives with them with spike in voltage before they expire. does this mean that a 100$ PSU will not fail. far from it, but the odds are when the good quality Psu fails it has safeties in place that prevents its failure to take out other components in their last breath

 

[madmatt30]

Using a CX as an example of a bad PSU isn't really a viable one IMO.
The cx 2012 isn't as bad as its tier rating on here makes it out to be.
To put it in tier 4 with some awful units that can takes out systems is unfair.
The CX is merely mediocre (or average) quality , its not a dangerous unit by any means , it can output its rated wattage fine.
By all accounts a kingwin, inwin , cit branded unit - they'll all be really bad no doubt about it.
Why??
Because many come with 500w labels & can only output 250-300w in real world terms.